1. Field of the Invention
This invention relates to linear electromagnetic machines such as linear motors, electrodynamic actuators, alternators and the like, and more particularly to a new and improved cylindrical laminated stator assembly for such machines and a new and improved method of making the same.
2. Description of the Related Art
Known prior art linear electrodynamic reciprocating machines include an outer stator surrounding an inner armature which reciprocates therein. A major problem in achieving efficient operation in such linear machines is optimizing the flux pattern and minimizing the eddy current losses in the stator. Eddy currents result in energy losses through undesired heat generation and aberrations in the magnetic flux. To reduce this problem, stators and armatures are of laminate construction which subdivide the electromagnetic forces such that the flux flows in smooth paths in planes parallel to the laminations.
A cylindrical construction is a preferred configuration for a linear electrodynamic reciprocating machines since it provides a uniform air gap between the stator and armature. The stator member of such a device usually includes a plurality of axially extending laminations, whose inner edges define a hollow cylindrical bore in which the armature reciprocates, and at least one circumferentially wound toroid-shaped coil.
Previously constructed cylindrical laminated stators for such machines are characterized by non-uniform laminations and variations in their spacing and alignment. For example, the flat laminations of U.S. Pat. Nos. 3,828,211 and 4,206,373 are deformed at their outer edges in an attempt to produce a tighter pack at both the inner and outer circumference. However, those configurations necessitates the use of assembly jigs, complex forming dies and undue working of the electrical grade iron used in the stator laminations. Tapered spacers have also been used between flat laminations, but it is difficult to insure a uniform arrangement at both the inner and outer circumference. An involute lamination construction, as described in U.S. Pat. No. 3,543,061 for example, has provided some improvement in the spatial and operating characteristics of laminated electromagnetic devices, yet still involves complex fabrication.
Furthermore, once the laminations are fixed together to form a stator assembly and removed from the assembly jig, a coil may still have to be throw-wound into the annular channels opening into the bore of the stator assembly.
All of the above previous manufacturing techniques are imprecise, non-uniform and very complex especially when a large number of laminations are desirable to reduce eddy current losses and produce higher efficiencies. The construction become especially difficult for miniature linear motors where, for example, the stator bore may be less than 0.5 inches in diameter and a plurality of coils are to be wound in the stator formed by the laminations.